Patent GB-678268-A (GB)
Title: Improvements in or relating to radio locating systems
IPC: G01S7/282
Filed: 1948-02-27
Abstract: 678,268. |Radiolocation. DEPARTMENT OF COMMERCE, DIRECTOR OF THE OFFICE OF TECHNICAL SERVICES OF. Feb. 27, 1948 [Nov. 26, 1946], No. 5994/48. Class 40 (vii). A pulse radar system employs a main type-A cathode - ray display, the time-base of which is controlled by a signal of the pulse recurrence frequency and a further expanded type-A display the timebase of which is controlled by a harmonic of the pulserecurrence-frequency signal, whereby a selected portion of the main display may be presented on the expanded display, thus enabling a more accurate range determination to be made. Further cathode-ray displays are also provided for the measurement of azimuth and elevation; these are synchronized by the harmonic-frequency signal. The output of oscillator 10 which synchronizes the transmission of pulses from transmitter 15 is applied to phaseshifter 20 and via frequency-multiplier 18 to phase-shifter 40. The complete rotation of the shaft of each phase-shifter produces a phasechange of 360‹ and, since the frequencymultiplier 18 generates the tenth harmonic of the pulse-recurrence frequency and the shaft 41 is made to rotate ten times for each rotation of the shaft 19 through the intermediary of the gear-box 44, one complete rotation of the shaft 19 alters the phase of the output from each phase-shifter by an amount corresponding to the interval between successive pulses. The output of phase-shifter 20 is applied via shaping circuit 22 to the saw-tooth generator 24 to produce the horizontal sweep for the fullrange oscilloscope 27. The output of phaseshifter 40 similarly controls the horizontal time-base sweep of the fine-reading range oscilloscope 35 via the units 50 and 53. The output of phase-shifter 40 also controls the time-base sweep for the elevation and azimuth oscilloscopes 36 and 37 via units 52 and 55 and units 51 and 54 respectively. The output from phase-shifter 20 is also applied to multi-vibrator 28, which delivers a square-wave signal of half the pulse-recurrence frequency to unit 30. The output of unit 30, which comprises a pulse signal of width equal to one cycle of the harmonic frequency is applied to the control grid of the cathode-ray tube 35 to illuminate the screen during one cycle of the harmonic cycle once in every two pulse-recurrence cycles. The output of unit 30 may also be applied to the control grid of cathode-ray tube 27 through an attenuator, Fig. 5 (not shown), to brighten the trace and indicate the portion of the total range display which is being presented on tube 35. As described, the screen of oscilloscope 35 is illuminated in alternate transmitted-pulse cycles only; if desired, the frequency-divider may be omitted so that the oscilloscope may be illuminated in each cycle. Echo signals received by receiver 47 are applied to the vertical deflecting plates of oscilloscopes 27 and 35 to produce two type-A displays. In operation, the shaft 19 is rotated by the hand wheel 9 until the selected echo indication is brought under the hair line on the screen of the oscilloscope 27. The echo indication will then be visible on the screen of the oscilloscope 35 and the hand wheel is further rotated until the echo indication is aligned with the hair-line across the screen of this oscilloscope, the range then being indicated on the counter 43. Signals from the azimuth receiver 47 are also applied to the vertical-deflecting plates of azimuth oscilloscope 37, to the horizontal-deflecting plates of which is applied a switching voltage from the unit 62 which controls the alternate operation of the aerials 68 in a switched-lobe system for determining direction in azimuth. A time-base voltage of the harmonic frequency and the output of unit 30 are also applied to oscilloscope 37, so that the display produced on the screen thereof is similar to that produced in oscilloscope 35 with each echo indication shown as a double pulse and the selected echo indication centred about the vertical hair-line across the screen of the oscilloscope. The aerials 68 are adjusted in azimuth until the two indications of the hair are of equal amplitude, when the azimuth of the selected echo signal is shown on a counter (not shown). A further system comprising aerials 66, receiver 46 and oscilloscope 36 is used to determine the elevation of the selected echo-producing target. In a modification, Fig. 6 (not shown), marker signals are used in place of the hair-lines used in oscilloscopes 27 and 35. The output of each phase-shifter is applied to a marker-pulse generator which is so phased to produce a marker-pulse indication at the centre of the horizontal time-base traces of the oscilloscopes 27 and 35. The output of each marker-pulse generator may be either positive or negative for application to the vertical deflecting plates of the respective oscilloscope; the output may alternatively be used to brighten the centre of the trace. In this system, phase-changes occurring in units 22 and 24 and units 50 and 53, due to alterations in the power supply or in the ambient temperature, may be compensated by arranging that corresponding changes occur in the phasing of the marker pulses. Specification 552,072 is referred to.